Semi-dull finish bobbin case basket



Oct. 17, 1967 N. PERRI 3,347,193

SEMI-BULL FINISH BOBBIN CASE BASKET Filed July 50, 1965 2 Sheets-Sheet lFIGZ.

N. PERRI Oct. 17, 1967 SEMI-BULL FINISH BOBBIN CASE BASKET 2Sheets-Sheet 2 Filed July 30, 1965 United States Patent 3,347,193SEMI-BULL FINISH BOBBIN CASE BASKET Nathan Perri, Northlake, Ill.,assignor to Union Special Machine Company, Chicago, 111., a corporationof Illinois Filed July 30, 1965, Ser. No. 476,060 7 Claims. (Cl.112--228) ABSTRACT OF THE DISCLOSURE This invention relates tolockstitch sewing machines and, more particularly, to improvements inthe rotary hook assembly used in such machines.

Lockstitch sewing machines employing rotary hooks which rotate on ahorizontal axis operate at high speeds in the neighborhood of 5000stitches per minute and in some instances at higher speeds. Whenoperating the sewing machine at these very high speeds, diflicultiestraceable to the rotary hook assemblies are encountered. The rotaryhook, which travels around a stationary bobbin case is mounted, musttake two revolutions to each forward movement of the sewing machineneedle through the throat of the throat plate which means that the hookrotates 10,000 or more revolutions per minute.

Rotary hook assembles of the type herein referred to are disclosed, forexample, in Covert and Schoij US. Patent No. 2,694,373, Nov. 16, 1954;and Attwood U.S. Patent No. 2,941,488, June 21, 1960. This type ofrotary hook assembly is used in various lockstitch sewing machines, anillustrative example of such a sewing machine being disclosed in CovertUS. Patent No. 2,977,910, Jan. 17, 1956.

A rotary hook assembly of the type mentioned above is mounted below thethroat plate of the sewing machine and, as is well known, it comprises,in general, a stationary bobbin case removably mounted within a centralopening of a surrounding bobbin case basket which in turn is mountedwithin a rotatable cup-like element which carries a loop engaging hookat its periphery. The hook directs the needle thread loop around theoutside of the bobbin case basket in a manner that casts the loop aroundthe bobbin thread. The bobbin thread travels from the bobbin spoolwithin the bobbin case to the workpiece above the plate, the initialloop of the needle thread being caught by the rotating hook immediatelyafter the needle has made its downward or forward stroke and has startedback on its upward or retraction stroke. While the needle is continuingits upward stroke and while it is up, the rotary hook directs the needlethread loop around the outside surface of the bobbin case basket, caststhe loop around the bobbin thread and the take-up means of the sewingmachine draws the loop up and around the bobbin thread to make thestitch, while the rotary hook makes an idle revolution, ready to repeatthe cycle to make a stitch upon the next reciprocating stroke of theneedle, all in a manner well known.

The rotary hook assemblies heretofore available have been constructed ofsteel and of various alloys. Usually the bobbin case baskets have beenplated or coated with a layer of wear resistant metal such as chromium.But

it is significant to note here that the parts or surfaces of the partsengaged by the loop thread during the operation of the heretoforeavailable rotary hook assemblies were smooth and frequently they werepolished to a mirrorlike finish.

One of the drawbacks of the hook assemblies heretofore available is thatat a very high speed of operation of the sewing machine, there is atendency of the thread loop to puff away at a terrifiic rate of speedimmediately after the hook beak has passed the 6 oclock position of therotary hook. As a frame of reference and for purposes of this discussionand description, it is assumed that the outer end of the rotary hookassembly is viewed as though one were looking at the face of a clock.During this puff away phase, the needle thread becomes utterlyuncontrollable; the loop assuming a balloon type shape at the highspeeds at which present day sewing machines are capable of operating.When then, an almost instantaneous increment of time later, the needlethread takeup mechanism on the sewing machine begins to rise with arapid acceleration for the purpose of drawing up the needle leg of thethread loop to draw up the loop, a heavy and sudden jerk will be exertedon the ballooning thread loop, which produces an effect in the thread asdoes the sudden jerking on the end of a piece of loose rope. In such acase, the rope will start to whip and flutter, whereby a drag effect iscreated against the pull. A similar action is created in the thread loopwhen using prior art rotary hook assemblies at very high speed ofoperation of the sewing machine. This drag effect causes an untimelytension build-up in the needle thread in the direction of the needlethread supply and the previously set stitch in the line of stitching. Asa result, thread is frequently drawn from the needle thread supply aheadof the proper time, causing loose stitch forming and pulling the loop upinto the throat plate, and this prevents relaxed, uniform stitches andoften causes the material of the workpiece being sewn to pucker in thezone of stitching.

Heretofore, there have been attempts made to overcome the unfavorableconditions in high speed operation mentioned above but with little, ifany, success. One remedy has been to increase the thread tension butthis results in unwanted puckering and frequent thread breakmg.

A principal object of this invention is to overcome the drawbacks ofprior art rotary hook assemblies of the kind discussed above and toprovide a rotary hook assembly which permits higher operating speedswhile at the same time permitting operation at lower thread tension thanprior rotary hook assemblies. This object is accomplished by providing asurface on the bobbin case basket which, instead of being smooth, ismodified to have a finish consisting of minute indentations andelevations, the latter being leveled and smoothed off, as by bufl'ing,so that the surface is made up of minute contiguous rolling hills andvalleys lying in random orientation and free of sharp peaks, jaggedprojections and sharp edges; and the surface has a semi-dull velvet-likefinish.

A rotary hook assembly, made according to the invention, and asdescribed in further detail hereinafter, reduces thread breakage, thecheck spring functions at the proper time and less check spring tensionis required. The needle thread does not whip between the guidingeyelets. It permits the needle thread to be drawn from the thread supplyat the proper time, that is, when the take-up is at the upper endportion of its stroke and when the stitch is being set in the fabric.And it produces relaxed, uniform stitches which reduces the likeli hoodof the stitches causing the fabric material to pucker in the zone ofstitching.

Although the novel features which are believed to be characteristic ofthe invention are pointed out in the annexed claims, the inventionitself as to its objects and advantages and the manner in which it maybe carried out, may be better understood by reference to the followingmore detailed description taken in connection with the accompanyingdrawings forming a part hereof, in which:

FIG. 1 is a front view of a rotary hook assembly constructed inaccordance with the invention including, in section, the throat plateand supporting plate, the sewing machine needle and a workpiece beingsewn;

FIG. 2 is a view partly in section looking from the rear to illustratethe movement of the needle thread loop when the loop reaches the 6oclock position, this view being taken on a vertical plane behind thebasket;

FIG. 3 is a view in perspective of the rotary hook assembly showing theneedle. thread loop just before it is cast off;

FIG. 4 is a front view in elevation of the bobbin case basket having thevelvet-like surface finish in accordance with the invention;

FIG. 5 is a plan view of the bobbin case basket shown in FIG. 4;

FIG. 6 is a view in perspective of the bobbin case;

FIG. 7 is a partial view in section greatly enlarged to illustrate thehills and valleys and the leveling off of the peaks of the hills on thesurface of the bobbin case basket; and

FIG. 8 is a view in section of a detail.

The rotary hook assembly, illustrated in the drawings, is substantiallythe same in construction as that disclosed in the above mentioned Covertet al. U.S. Patent No. 2,694,373; but with this significant difference:the bobbin case basket, instead of being smooth and polished to amirror-like finish, has been subjected to a particular sand blasttreatment and to a buffing so that is surface has a semi-dull appearanceand consists of minute indentations and elevations and the roughenedsurface has been buffed to remove any sharp peaks or jagged projectionsthat may have been left on the surface of the elevations or hills afterthe sand blasting treatment.

Referring now to the drawings in which like reference charactersindicate similar parts throughout the several views, the rotatingcomponent of the rotary hook comprises a generally cup-shaped spidermember having a hub extension 21 secured by means of set screws 22 tothe forward end of hook driving shaft 23. One end of the rim member 20ais provided with a forwardly and outwardly extending hook point portionor beak 24 which serves to seize and carry the needle loop in a mannerto be described hereinafter. The inner surface of the rim of member 20is provided with a raceway 36 for receiving the bobbin case basket ribor rail 25 and for guiding the rim portions of the rotary component 20in its travel about the hook basket 40.One-portion of the raceway isprovided by an overhanging or inturned lip 26 formed on detachablecurved rim member 27 which is secured to the rim of the cup-shapedrotary component 20 by screws 28 (see FIG. 3). The end of the detachablemember 27 adjacent hook point 24 is formed as a trailing thread guidingprojection 29. Another portion of the raceway is formed by a lip 30formed on the inner surface of the rim of member 20 adjacent the base ofhook point 24. Mounted on the outside of the rim of member 20, on theopposite side thereof from detachable member 27 and fastened to member20 by screws 31, is a guide plate 32 having one end thereof adjacenthook point 24 formed as a forwardly and inwardly extending pointed spur33: spaced from the base of hook point 24 and affording a throat 71 forreceiving needle thread loops seized by hook point 24. The throat 71terminates in a pointed generally V-shaped crotch 72 which the loopthread engages as the hook point travels through an arc of about 180after it seizes the loop. This spreads the legs LS and LN of the loop toassist in carrying it around the basket 40.

Plate 32 provides a needle loop engaging flange having an outer edge 34curved generally outwardly from the hook point 24. The outer curved edge34 guides the leg LS of the needle thread loop over the outer face ofthe bobbin case basket. The extremity of plate 32 is provided with aneedle clearing notch 35 (FIG. 3).

The stationary component of the rotary hook assembly comprises a bobbincase basket 40, shown separately in FIGS. 4 and 5 and a bobbin case,shown separately in FIG. 6. A rotatable bobbin spool, not shown, ismounted in the hollow of the cylindrical portion 60, for rotation on asleeve of the bobbin case which surrounds pin 44 of the basket 40.

Referring now particularly to FIGS. 4 and 5, the bobbin casebasket isformed with an angular, cup-like body member 42 provided at its bottomor inner end with a cross bar 43 arranged to support an axially disposedpin 44 extending from the inner to the outer end of the cupshaped member42. Pin 44 is provided with an annular notch 45 adjacent the roundedouter end thereof. The notch 45 is indicated in FIG. 4 by the brokenline circle. Bobbin case basket rail 25 is formed as an annular rib ofthe hollow body member 42 and is provided with a gap 26 (FIGS. 1 and 3)is drawn away from the bobbin case basket 40 just in advance of itspassage over the inner leg of the needle thread loop, thus facilitatingpassage of the needle thread around the bobbin case.

A radially extending flange 47 is formed at the outer end of the bobbincase basket and extends along approximately three quarters of thecircumference thereof; a portion 54 positioned to the left of aretaining notch 48 and a portion 58 to the right of this notch, saidportion 58 having cut out portions 37, 38, 39. Flange 47 is formed atthe outer end of the bobbin case basket and the retaining notch 48 isadapted to mate with a lug or finger 49 mounted on bobbin case retainerbar 50 (FIGS. 1 and 3), in turn mounted on a screw post 50a fastened tothe bed or frame of the machine. The lug 49 mating in the notch 48serves to prevent the bobbin case 41 and bobbin case basket 40 fromrotating with the rotary component of the hook assembly during operationof the machine. Flange 47 is also provided with a needle opening 51behind notch 48. Opening 51 is arranged to permit entrance of needle 52(FIG. 1) into the rotary hook assembly so that a needle loop may beformed upon the initial movement of the needle after the needle hasreached the end of its downward stroke. The needle thread loop is pickedup by hook beak 24, as is well known in the art.

As illustrated in FIG. 1, bobbin thread b emerges from the bobbin case,passes through an eyelet in the cylindrical wall of the bobbin case,then under a spring 75, and is guided by an inturned flange lug a andthen passes through eyelet 53 mounted on the bobbin case. The bobbinthread b then passes upwardly across the radially extending faceof aportion 54 of flange 47 through the aperture 55 in throat plate 56 tothe workpiece 79, where, together with the needle thread loop, thestitches are formed. When bobbin thread b becomes slack, as during atacking operation, it is supported by peripheral face 57 of the portion54 of flange 47 to the left of notch 48. By constructing portion 54 ofthe flange 47 with sufiicient radial width and circumferential extentand suflicient thickness, slack bobbin thread will be held by the radialand peripheral faces thereof so that such thread will not enter the pathof hook point 24. The width of flange 47 is this area, i.e., the radialwidth of portion 54 is preferably made sufliciently great that bobbinthread I) is carried upward along the outer radial face of said portionto a point above the path of rotation of hook point 24. The thickness ofportion 54 of flange 47, i.e., the axial width of surface 57 ispreferably made sufliciently great that a minimum practical clearancebetween the inner. surface of flange 47 and hook point 24 is provided.

In FIG. 8, which is a cross sectional view through portion 54 of flange47, it will be seen that bobbin thread b when slack, rests on peripheralface 57 in its path to the work and hence cannot fall into the path ofhook point 24.

As has been indicated hereinbefore, the surface of the bobbin casebasket 40 is not smooth, as in bobbin case baskets heretofore used, butthe surface has been given a treatment that produces a surface thatconsists of minute elevations and indentations in the form of Contiguousminute hills and valleys in random orientation; the peaks of the hillsbeing leveled off and any sharp or jagged projections and sharp edgesbeing removed, as by a bufling operation, thus producing a surfacehaving a semi-dull appearance and a hard but velvet-like feel. Furtherdetails regarding this surface and the manner of producing it aredescribed later on herein.

The bobbin case 41, which is shown separately in FIG. 6, comprises asubstantialy closed cylindrical body member 60 having a rear open endand a substantially closed outer end 61 from which projects inwardly atubular axial post (not shown) which is adapted to fit on pin 44 of thebobbin case basket, the inner end of which engages an annular shoulder62 (FIG. 4) at the base of pin 44. The axial tubular post of the bobbincase serves for rotatably mounting the bobbin spool thereon, within thecylindrical wall of body member 60.

The upper portion of the body member 66 is provided with a cut-outsegment 63, which in the assembled rotating hook, is disposed belowopening 51 and arranged to admit the needle 52.

Closed outer end 61 of body member 60 is provided with a pair ofparallel undercut guide ribs 64, 64a to which are fitted opposite edgesof a spring pressed latch plate 65. Latch plate 65 is provided with anaperture 66, one end of which is adapted to mate with notch 45 of pin 44(FIGS. 1 and 5) thereby to hold the bobbin case within the centralopening of the bobbin case basket. A lever plate 67, having an aperture68, is hingedly mounted at one end thereof on one end of latch plate 65so that when lever plate 67 is swung on its hinge, away from latch plate65, the latch plate is disengaged from notch 45 in pin 44, permittingremoval of the bobbin case 41 from the bobbin case basket 40. When thebobbin case is inserted in the bobbin case basket, a latch 60 (FIG. 1)located at one end of latch plate 65, engages the sides of a notch 70'in flange 47, thus preventing rotation of the bobbin case within thebobbin case basket.

A thread slit, not shown, in the drawing extends from the inner edge ofbody member 60 to an aperture in the cylindrical side wall of member 60,the aperture being hidden in FIG. 6 by a thread tension spring 75.Thread from the bobbin passes through the aperture in Wall 60 beneathspring 75, through a guide formed by inturned prong 75a of the springalong the outer surface of the wall of body member 60' and through selfthreading eyelet 53. The bobbin thread b then passes over the exposedportions of the flange 47 as described above. The eyelet is mounted in arecess portion 76 of closed end 61 (FIG. 6) by means of screw 77. Thethread carrying portion of eyelet 53 fits into a recess 78 (FIG. 1) inportion 54 of flange 47. Recessing eyelet 53 in this maner permitspassage of the needle thread around the front end of the bobbin case.Now it will be seen that bobbin thread b (FIGS. 1 and 3) is protectedfrom hook point 24 by eyelet 53 and portions 54 and 57 of flange 47.Thus eyelet 53 and that portion of flange47 located on the left of notch48 form a guarding means for the bobbin thread b which substantiallyeliminates breakage of the bobbin thread by the hook point or beak 24.

Referring again to the bobbin case basket, as shown in FIGS. 4 and 5,the shape and construction is of a standard type except that the basketdoes not have a smooth surface. It has a surface, which is accordancewith the present invention, consists of contiguous minute hills andvalleys in random orientation and free from sharp peaks, jaggedprojections and sharp edges. The preferred way of producing a bobbincase basket as illustrated in FIGS. 5 and 6 is to start with a standardbasket made of steel that has been chromium plated in conventionalmannear, the basket having a conventional smooth surface. Thisconventionally produced bobbin case basket was then subjected to a sandblasting treatment. The sand blasting material used was size 240 gritFlint-shot at an air pressure of 40 p.s.i. (pounds per square inch) andthe particles were impacted against the surface until the chrome platingwas substantially all removed; this requiring approximately one minute.This produced a surface on the basket which consisted of contiguousminute elevations and indentations in random orientation, and not ofuniform sizes. Some of the peaks of the elevations were sharp and someof exposed edges were sharp or had minute jagged projections. The soroughened, sand blasted surface was then buffed on a soft bufiing wheelsufficiently to remove the jagged peaks and projections produced by thesand blasting. The bufling was carried out until the final finish of aroughness approximately 60-80 micro-inch (R.M.S.) was achieved.Reference is made to FIG. 7 which is a vertical cross section to greatlyenlarged scale to illustrate the contiguous minute hills h and valleys vof varying sizes and distributed over the surface in random orientationand in which any sharp peaks have been leveled off by bufiing thesurface after the sand blasting treatment. Such a surface resulting fromthe sand blasting treatment with fine sand or grit shot and thereaftersubjected to bufling to produce a final finish having a roughness rating60-80 micro-inches (R.M.S.) is herein, and in the claims, for purposesof convenience of description, referred to as a velvet-finish.

Operation of the rotary hook assembly will now be described andthereafter, data obtained from tests con ducted with the known orstandard rotary hook assembly having a chrome plated smooth bobbin casebasket, and tests conducted under like conditions with a rotary hookassembly, having a bobbin case basket having the velvetfinish abovedescribed; these tests showing the very material improved resultsattributable to the invention.

In operating the rotary hook, needle 52 descends through aperture 55 inthroat plate 56 and through opening 51 into the upper portion of thebobbin case basket, which remains stationary. As the needle begins andthen continues its upward or retraction stroke, a loop of needle threadis cast into the path of the rotating hook point 24, in a manner wellknown in the art. The needle thread loop is caught in the throat 71 andthe thread engages the crotch 72 of the rotating component 20 of theassembly; this crotch spreading the legs LS and LN of the loop. Thecrotch, as it continues in its circular path of travel, carries the looparound the periphery of the basket in the arc to the left of notch offlange 47, as viewed in FIG. 1. When the crotch 72 reaches the 6 oclockposition (at the bottom of the hook assembly) the loop is in a position,as illustrated in FIG. 2. As the crotch continues in its rotary path theloop is released from the crotch and the needle thread take-up mechanismon the sewing machine (which is not illustrated in the drawing) hasbegun to draw the excess needle thread upward at a rate exceeding theangular speed of the hook point 24. When the point 24 has reached theposition illustrated in FIG. 3, the loop is caught on the projection 29of member 20a and the leg LS has been guided inside the retainer arm 50through notch 48 and finally the leg LN of the loop is drawn up and theloop, now around the bobbinthread b, is drawn up to form. the lockstitch80. The rotary component 20 then makes an idle revolution after theneedle thread is withdrawn therefrom, after which the stitch formingcycle than that of the conventional smooth, polished finish. Also, theraceway of the rotating component moves over the rail of the basket in adecidedly smoother manner than in conventional hooks. This is especiallyimportant is repeated to make the next stitch. at the moment when thefront leg (LS in the drawings) The following Tables I and II show dataobtained in is being pulled out of the basket retainer finger recess.tests to compare the operation of a conventional hook as- Although inthe foregoing description only the bobbin sembly having a smooth surfacebobbin case basket with case basket has been disclosed as having thesurface the operation of a hook assembly, according to the inventreatedto provide the velvet finish, it will be understood tion, having avelvet finish as described above. The tests that the face of the bobbincase may be treated to prowere conducted on the same sewing machine andthe test vide a velvet finish. In fact, any surface of any part of hookassemblies were the same except for the differences the assembling wherethe part moves in contact with mentioned. Hooks identified in the tablesas A and B and relatively to another or where the thread moves in wereconstructed according to the invention and hooks sliding contact with, asurface, improved operation may identified as C and D were conventional.be effected by providing the velvet finish thereon.

TABLE I Hook A Hook B Bobbin Check Needle Bobbin O..ec Needle TensionSpring Thread Tension Spring Thread (02.) (02.) (02.) (02.) (02.) (02,.)

% 1 2 1 2 M 1 M 1 $4 1 M 1 l4 1 M 1 M M 1 M 1 TABLE II Hook A H00 13Bobbin Check Needle Bobbin Check Needle Tension Spring Thread TensionSpring Thread (02.) (02.) (02.) (02.) (02.) (02.)

70/2 Soft 1 3 l 3 3/0 Nylon 2 2 2-5 Nylon. M /2 1% 2 00 Nymm Unable tosew Unable to sew 000 Nymo Unable 5o sew Unable to sew In the abovetables the size and kind of thread is shown, and the bobbin thread,check spring and needle thread tensions are shown. The data in eachinstance was taken after the sewing machine was operating at 5400 r.p.m.After each hook was installed and sewing with a good stitch, tackingability, etc., a check was made of the bobbin thread tension, checkspring, and needle thread ten- SlOl'l.

The data in the tables show that when using a 70/2 soft cotton needlethread, it required 3 oz. of needle thread tension on a machine equippedwith a conventional hook, whereas only 2 oz. of needle thread tensionwas required to sew the same thread on a machine equipped with the hookconstructed according to the invention. Also, it will be observed thatwhen sewing synthetic threads (nylon, Nym-o), a much lower needle threadtension is required to sew the same synthetic threads on a machineequipped with a hook made according to the invention. This accounts forless thread breakage when using the hook assembly of the invention.

In the operation of the hook assembly provided by the invention, thethread loop when pulled around the 9 oclock position of the basketencounters less frictional resistance, and the thread loop, afterpassing through the 6 oclock position, does not putt and balloon awaybut stays rather close to the periphery of the basket, following samearound in a gradual manner. Since the loop does not balloon out, thejerk of the rising take-up will not cause whipping or fluttering of thethread, and consequently, the unwanted drag effect, described in theforegoing, will not occur.

Furthermore, the velvet finish eliminates any sharp edges on the basketwhich is another friction reducing factor with regard to the threadloop. In other words, the

coefficient of friction of the velvet finish areas is less.

And, although the preferred method of producing the velvet finish is bya sand blasting treatment as described above, other methods of producinga light roughened finish may be employed, such, for example, asimmersing I the part to be treated in a mineral acid such ashydrochloric or sulphuric, the time of immersion and concentration ofthe acid being adjusted to bring about the desired etching, after whichthe etched surface may be lightly buffed. Or the .part may be roughenedin an electrolytic cell having positive and negative electrodes andcontaining a suitable electrolyte through which electric current ispassed; the part to be roughened serving as anode. The amount ofroughening can be controlled by adjusting the time and amount of currentpassing through the electrolyte or the desired velvet finish surface maybe produced in other ways.

The terms and expressions which have been employed herein are used asterms of description and not of limitation, and there is no intention inthe use of such terms and expressions of excluding any equivalents ofthe features shown and described or portions thereof,but it isrecognized that various modifications are possible within the scope ofthe invention claimed.

What is claimed is:

1. A rotary hook assembly for a lockstitch sewing thread engaging flangeadjacent to and guiding the needle thread lo'op over said face, guidemeans for guiding thread from said bobbin over said flange, said hookmeans carrying said needle thread loop around said bobbin case basket toloop it over said bobbin thread, the surfaces of said bobbin case basketwhich are engaged by said loop thread having a semi-dull finishconsisting of contiguous minute hills and valleys in random orientationfree from sharp peaks jagged projections and sharp edges and having ahard but velvet-like feel, said semi-dull finish being characterized bya coefficient of friction substantially less than that of a smooth,polished finish.

2. A rotary hook assembly according to claim 1 in which said surfaceshave a roughness rating of 60-80 micro inches.

3. A rotary hook assembly for a lockstitch sewing machine comprising acup-shaped rotary component having a rim portion mounting a needlethread loop engaging hook means rotatable in a circular path, said rimportion having a raceway on its interior surface, a bobbin case basketmounted in said cup-shaped rotary component, said basket having agenerally cylindrically shaped wall, a bobbin case mounted within saidbasket, said basket having a vertically disposed portion at its rear endand a central opening at its front end and having a thread loop guidingflange at the front end of said cylindrical wall engaged by the loopthread during a stitching operation When said rotary component isrotated and said cylindrically shaped wall having an interrupted guiderail around its periphery, said raceway fitting over said guide rail andmoving in contact therewith when said rotary component is rotated, thesurface of said basket in those areas Where it contacts the needle loopthread and Where it engages said rotary component in frictional contacthaving a semi-dull finish and hard but velvet-like feel comprisingcontiguous, minute hills and valleys positioned in random orientationfree from sharp peaks, jagged projections and sharp edges, thefrictional resistance of said areas to the passing of said needle threadloop thereover being substantially less than that of a smooth, polishedfinish.

4. A rotary hook assembly for a lockstitch sewing machine comprising acup-shaped rotary component having a rim portion mounting a needlethread loop engaging hook means rotatable in a circular path and havinga raceway on the interior surface of said rim portion, a bobbin casebasket mounted in said cup-shaped rotary component, said basket having agenerally cylindrical shaped wall, a bobbin case mounted within saidbasket, said basket having a vertically disposed portion at its rear endand a central opening at its front end, said basket having a thread loopguiding flange at the front end of said cylindrical wall engaged by theloop thread during a stitch forming operation and said cylindricallyshaped wall having an interrupted guide rail around its periphery, saidraceway fitting over said guide rail and moving in contact therewithwhen said rotary component is rotated, the surface of said basket inthose areas where it contacts the needle loop thread and where itengages said rotary component in frictional contact having a finishcomprising contiguous, minute hills and valleys positioned in randomorientation free from sharp peaks, jagged projections and sharp edgesand having a roughness rating of 60-80 micro inches.

5. A bobbin case basket in a rotary hook assembly for a lockstitchsewing machine comprising a cup-shaped rotary component having a rimportion mounting a needle thread loop engaging hook means rotatable in acircular path and having a raceway on the interior surface of said rimportion, a bobbin case basket mounted in said cupshaped rotary componentand a bobbin case therein, which bobbin case basket comprises agenerally cylindrical shaped wall within which said bobbin case may bemounted, a vertically disposed rear Wall portion at the rear end of saidcylindrical wall and a central opening at its front end, said baskethaving a thread loop guiding flange at the front end of said cylindricalwall engaged by the loop thread and said cylindrically shaped wallhaving an interrupted guide rail around its periphery adapted to fitinto said raceway in frictional contact therewith when said rotarycomponent is rotated, said basket having a finish over its interior andexterior surfaces comprising contiguous, minute hills and valleyspositioned in random orientation buffed sufliciently to be free fromsharp peaks, jagged projections and sharp edges, and having a hard butvelvetlike feel, said finish being characterized by a coefiicient offriction which is substantially less than that of a smooth, polishfinish.

6. A bobbin case basket in a rotary hook assembly for a lockstitchsewing machine comprising a cup-shaped rotary component having a rimportion mounting a needle thread loop engaging hook means rotatable in acircular path and having a raceway on the interior surface of said rimportion, a bobbin case basket mounted in said cup-shaaped rotarycomponent and a bobbin case therein, which bobbin case basket comprisesa generally cylindrical shaped wall within which said bobbin case may bemounted, a vertically disposed rear wall portion at the rear end of saidcylindrical wall and a central opening at its front end, said baskethaving a thread loop guiding flange at the front end of said cylindricalwall engaged by the loop thread during a stitch forming operation andsaid cylindrically shaped wall having an interrupted guide rail aroundits periphery, and adapted to fit into said raceway in frictionalcontact therewith when said rotary component is rotated, said baskethaving a sand-blasted finish over its interior and exterior surfacescomprising contiguous, minute hills and valleys positioned in randomorientation buffeed sufiiciently to be free from sharp peaks, jaggedprojections and sharp edges to provide a semi-dull, velvet finish whichis less resistant to the passage of said needle loop thread thereoverand in contact therewith than a smooth, polished finish.

7. A bobbin case basket in a rotary hook assembly for a lockstitchsewing machine comprising a cup-shaped rotary component having a rimportion mounting a needle thread loop engaging hook means rotatable in acircular path and having a raceway on the interior surface of said rimportion, a bobbin case basket mounted in said cup-shaped rotarycomponent and a bobbin case therein, which bobbin case basket comprisesa generally cylindrical shaped wall within which said bobbin case may bemounted, a vertically disposed rear wall portion at the rear end of saidcylindrical wall and a central opening at its front end, said baskethaving a thread loop guiding flange at the front end of said cylindricalwall engaged by the loop thread during a stitch forming operation andsaid cylindrically shaped wall having an interrupted guide rail aroundits periphery, and adapted to fit into said raceway in frictionalcontact therewith when said rotary component is rotated, said baskethaving a sand-blasted finish over its interior and exterior surfacescomprising contiguous, minute hills and valleys positioned in randomorientation buffed sufliciently to be free from sharp peaks, jaggedprojections and sharp edges and having a hard but velvet-like feel and aroughness rating of 60-80 micro inches.

References Cited UNITED STATES PATENTS 1,610,927 12/1926 Butler 51-3191,697,810 1/1929 Comstock 51-319' X 2,694,373 11/1954 Covert 112228 X2,941,488 6/1960 Attwood 112-228 2,977,910 4/1961 Covert 112256 PATRICKD. LAWSON, Primary Examiner.

HERBERT F. ROSS, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,347,193 October 17, 1967 Nathan Perri It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 1, line 32, after "case" insert basket in which the bobbin casecolumn 6, line 6, for "is" read in columns 7 and 8, TABLE II, in theheadings, for Hook A" and "Hook B" read Hook C and Hook D same TABLE II,second and third columns, line 5 thereof, for 50" read to column 10,line 20, for "cup-shaaped" read cup-shaped Signed and sealed this 22ndday of April 1969.

(SEAL) Attest:

Edward M. Fletcher, Jr. EDWARD J. BRENNER Attesting Officer Commissionerof Patents

1. A ROTARY HOOK ASSEMBLY FOR A LOCKSTITCH SEWING MACHINE COMPRISING AHOLLOW CUP-SHAPED ROTARY COMPONENT HAVING A RIM INCLUDING A NEEDLETHREAD LOOP ENGAGING HOOK MEANS ROTATABLE IN A CIRCULAR PATH, ASTATIONARY BOBBIN CASE BASKET HAVING A CENTRAL OPENING AND MOUNTEDWITHIN SAID CUP-SHAPED ROTARY COMPONENT, A BOBBIN CASE ENCLOSING AROTATABLE BOBBIN MOUNTED IN SAID CENTRAL OPENING, SAID BOBBIN CASEHAVING A FACE PORTION, SAID BOBBIN CASE BASKET HAVING A PERIPHERALLYEXTENDING LOOP THREAD ENGAGING FLANGE ADJACENT TO AND GUIDING THE NEEDLETHREAD LOOP OVER SAID FACE, GUIDE MEANS FOR GUIDING THREAD FROM SAIDBOBBIN OVER SAID FLANGE, SAID HOOK MEANS CARRYING SAID NEEDLE THREADLOOP AROUND SAID BOBBIN CASE BASKET TO LOOP IT OVER SAID BOBBIN THREAD,THE SURFACES OF SAID BOBBIN CASE BASKET WHICH ARE ENGAGED BY SAID